An action in a sentence can be represented in two ways, namely active and passive voice.
The passive voice always uses the past participle form of the main verb irrespective of any tense. Only the auxiliary verbs depend upon the sentence given in active voice.
The given sentence is in the active voice.
The correct answer is A) Are mixed
Option A) is correct as the sentence is in the simple present tense.
Options B, C, and D are not correct as the sentence does not indicate the future, the past and is in the simple present tense respectively.
It should be served very hot.